Sized partially esterified paper and its method of preparation



United States Patent @fifice 3,052,679 SEZED PARTHALLY ESTERIFKED PAPERAND ITS METHGD F PREPARATION Lloyd E. Herdle and Gordon C. Milligan,Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporationof New Jersey No Drawing. Filed Feb. 6, 1961, Ser. No. 87,107 5 Claims.(Cl. 117-46) This invention relates to partially esterified fiber papersized with a modified polyvinylacetate latex size, its preparation andbaryta coated photographic paper made therefrom.

It has been previously recognized that it is advantageous for paper ofgood dimensional stability that up to half of the hydroxyl of thecellulose fibers employed in its preparation be replaced by lower fattyacid radicals. Paper of this type as a base for photographic paper isdescribed in application Serial No. 755,418 of George A. Richter andLloyd E. Herdle. Many of the properties of paper are improved by tubsizing or surface sizing the paper. However, when partially esterifiedfiber paper is sized with cornmonly employed sizing materials a surfaceis obtained to which baryta coatings adhere poorly and which surfacelacks in smoothness or other characteristics.

One'object of our invention is to provide a surface size or tub sizeuseful for sizing partially esterified fiber paper. Another object ofour invention is to provide partially esterified fiber paper to which abaryta layer Will adhere and which exhibits good smoothness underallnormal conditions. A further object of our invention is to provide apartially esterified fiber paper having good water resistivity. A stillfurther object of our invention is to provide a partially esterifiedfiber paper whose surface has been sized with a polyvinylacetate layercontaining hydroxyethyl cellulose, plasticizer and Quilon chrome complexhardener. A still further object of our invention is to provide aphotographic paper having good dimensional stability, improved physicalstrength, resistance to penetration by water, good surface propertiesand which is inert to photographically sensitive emulsions. Otherobjects of our invention will appear herein.

We have found that desirable characteristics are imparted to partiallyesterified fiber paper by surface sizing the paper with a modifiedpolyvinylacetate latex which latex contains hydroxyethyl cellulose,plasticizer and Quilon chrome complex hardener. The partially esterifiedfiber paper is one in which 350% and desirably 840% of the hydroxyls ofthe cellulose fiber therein have been reacted with lower fatty acidradicals such as radicals of fatty acids of 24 carbon atoms. Paper ofthis type, which has been improved by internal sizing such as withcationic thermosetting polyamide-epichlorohydrin resin as described inU.S. Patents Nos. 2,926,154 and 2,926,116 of Keim and marketed byHercules Powder Co. under the name Kymene is especially adapted toprepare a sized paper in accordance with our invention. Paper the fibersof which have been partially acetylated as described in Richter andHerdle application Serial No. 755,418 will be referred to herein as PApaper.

The tub sizing of PA paper in accordance with our invention may beconveniently performed by passing the paper after its formation andafter drying through a bath of modified polyvinylacetate latex as willbe described herein. The paper thus sized is preferably passed throughsqueeze rolls or other means to reduce the size content to 0.1-3 partsand preferably 2 parts (dry weight) of polyvinylacetate per 100 parts ofcellulose. The paper is then dried such as by passing over heated rollsat a temperature of 125150 F., preferably followed by calendering.Although higher temperatures up to 295 may be employed, it appearsadvantageous to dry the paper at lower temperatures as represented bythe 125 150 F. range.

The composition of the modified polyvinylacetate latex used for tubsizing is composed of latex containing polyvinylacetate, plasticizer,hydroxyethyl cellulose and Quilon chrome complex hardener all dispersedin water. .It is desirable that the water to polyvinylacetate ratio be6-12z1. With too high a concentration of polyvinylacetate the latex maybe too thick for good operations. It is desirable to have a small amountof hydroxyethyl cellulose present as a protective colloid in the latexsuch as 0.5 5% of hydroxyethyl cellulose based on the weight of thepolyvinylacetate. The presence of a plasticizer compatible with thelatex is desirable. The concentration of plasticizer is not critical but335% thereof desirably 5-25% and preferably about 10% based on thepolyvinylacetate can be conveniently used. The use of plasticizer inminimum proportion contributes to good surface smoothness of the paperand avoids roughness upon rewetting. The plasticizers which have beenfound to be particularly useful are the aliphatic esters of dicarboxylicacids such as the phthalates, adipates and the sebacates. Someplasticizers of this type are dibutyl phthalate, dibutyl sebacate,methoxyethyl phthalate, dibutyl adipate,

4 di-2 ethylhexyl phthalate, dioctyl sebacate, and the like.

However, plasticizers illustrated by the butyl ether of diethyleneglycol acetate are particularly useful in this connection. Quilon chromecomplex is added in small proportion such as 1-10% based on the weightof the polyvinyl acetate. Quilon, which is a product marketed by the DuPont Company, is a water soluble Werner type chromium complex (Whosepreparation is described in US. Patent 2,273,040 of Her) dissolved in analiphatic alcohol (isopropanol). This complex may be a stearic acidcomplex or a myristic acid complex or the complex of chromiumoxychloride with some other fatty acid of at least 10 carbon atoms.

Paper tub sized as described herein is useful as the base forphotographic paper. For instance the paper so prepared may be barytacoated such as by applying thereto a coating of barium sulfate in anaqueous solution of gelatin in the conventional manner whereupon agelatin-silver halide photographic emulsion layer may be appliedthereover.

It appears that particularly good paper properties are obtained insizing paper in accordance with our invention if the paper afterapplying the size thereto is first subjected to drying at a lowtemperature such as about F. followed by raising the temperature tocomplete moisture removal from the paper.

The following examples illustrate our invention:

Example 1 Paper of 31 lbs. basis weight (31 lbs. per 1000 sq. ft.) madefrom kraft fiber which had been partially acetylated to approximately21% acetyl content and internally sized with a cationic thermosettingpolyamide-epichlorohydrin resin (such as that marketed by HerculesPowder Company under the trade name Kymene 557) was tub sized by passingthrough a sizing bath as described below for 5 seconds at 70 F. anddried for 4 minutes at 125 F. The sized paper was supercalendered using4 nips at F. and 30 psi. pressure. The composition sizing of the sizingbath was (parts being by weight): 100 parts of Patented Nov. 6, 1962 3had been prepared by adding the dibutylphthalate to the latex, allowingto stand for 24 hours, and then diluting with water and Quilon. Theproperties of the sheet so prepared were compared with a sheet preparedin the same manner except that no surface sizing was used. Tests showedthat the sized paper had substantially the same properties as theunsized paper except that it was resistant to water penetration whereasthe unsized paper was completely penetrated. The test results were asExample 2 The above procedure was repeated except that paper of 27 lbs.basis weight was used and the sizings employed were not only asdescribed in Example 1 but on various other samples of the paperpolyvinylacetate latex (without Quilon and plasticizer), gelatin,acrylic latex, styrene butadiene latex, polystyrene latex or no latex atall were respectively applied. The results obtained were as follows:

Paper of Iii-21% acetyl content and internally sized with Kymene SurfaceSize Cobb Size Measure of Baryta Surface H BuOH Dektol Uncal. Cal. Wetand Redry Gelatin 0.140 0. 259 0. 402 8. 4 9. 6 5. 8 PVAc 0.157 0.262 0.518 8. 8 8. 2 8. 4 PVAe-l-Q-l-DBP--- 0. 108 0.132 0. 113 0. 7 3.1 5. 4Acryhc latex Complete Penetration stlylene-butadiene Partial Penetration3. BX. Polystyrene latex-.. Complete Penetration None 0.157 0.278 com.

pen.

1 Buty1a1eoho14% in water.

The mixture of polyvinylacetate, Quilon and plasticizer offeredsubstantial advantage in resistance to penetration of water, butylalcohol solution and Dektol photographic developer solution. Because ofimproved resistance to water and butyl alcohol a baryta coated surfaceon this paper is smoother than that obtained using other sizingmaterials. The resistance to water and Dektol developer also contributesto faster photographic processing and drying.

The Cobb size test measures the effectiveness of the sizing of a sheetof paper. Essentially a liquid is permitted to remain in contact with100 cm. of surface area of the paper for an interval of time. The excessliquid is blotted off and the gain in weight is measured. The gain inweight in grams/100 cm. is the Cobb size value. The time of contact was2 min. for the water and the Dektol developer (1:1 in water); for thebutyl alcohol (4% in water) the contact time was 5 min.

The baryta surface measurements were made on a Surfanalyzer. Thisinstrument measures the shadow pattern cast by the surface whenilluminated by a light 4 from the horizontal. The values are relativewithin a given frequency range and sensitivity setting. For thenoncalendered paper (uncal." in the table) and the supercalendered paperwet for 20 min. and dried (wet and redry in the table) the frequencysetting was 0-2000 c.p.s. with a sensitivity setting of 775 and afrequency setting of 200-2000 c.p.s. with a sensitivity setting of 795,respectively. At these settings an uncalendered surface with aSurfanalyzer reading of 0.7 would be considerably smoother than anuncalendered surface with a reading of 8.4 but would be rougher than acalendered surface with a reading of 8.4 because of the greatersensitivity of measurement for the calendered surface.

We claim:

1. Paper, 350% of the hydroxyl of the cellulose fibers of which has beenreplaced by lower fatty acid radicals, which paper has a polyvinylacetate surface sizing which contains hydroxyethyl cellulose,plasticizer and watersoluble Werner type chromium complex in which atrivalent nuclear chromium atom is co-ordinated with an acycliccarboxylic acid group having at least 10 carbon atoms.

2. Paper, 3-50% of the hydroxyl of the cellulose fibers of which hasbeen replaced by lower fatty acid radicals, internally sized with acationic polyamide-epichlorohydrin resin, which paper has a polyvinylacetate surface sizing which contains hydroxyethyl cellulose,plasticizer, and water soluble Werner type chromium complex in which atrivalent nuclear chromium atom is co-ordinated with an acycliccarboxylic acid group having at least 10 carbon atoms.

3. Paper, 350% of the hydroxyl of the cellulose fibers of which has beenreplaced by acetyl, which paper has a polyvinyl acetate surface sizingwhich contains hydroxyethyl cellulose and water soluble Werner typechromium complex in which a trivalent nuclear chromium atom isco-ordinated with an acyclic carboxylic acid group having at least 10carbon atoms.

4. Paper, 350% of the hydroxyl of the cellulose fibers of which has beenreplaced by lower fatty acid radicals, which paper has a polyvinylacetate surface sizing which contains hydroxyethyl cellulose,plasticizer and watersoluble Werner type chromium complex in which atrivalent nuclear chromium atom is co-ordinated with an acycliccarboxylic acid group having at least 10 carbon atoms, and a coatingthereon of barium sulfate and gelatin.

5. A method of preparing paper useful for photographic purposes whichcomprises surface sizing paper, 350% of the hydroxyl of the cellulosefibers of which have been replaced by lower fatty acid radicals, with anaqueous solution of polyvinyl acetate containing hydroxyethyl cellulose,plasticizer, and a Water-soluble Werner type chromium complex in which atrivalent nuclear chromium atom is co-ordinated with an acycliccarboxylic acid group having at least 10 carbon atoms followed by dryingof the paper by means of heated rolls.

References Cited in the file of this patent UNITED STATES PATENTS2,887,429 Griggs et al. May 19, 1959 2,925,340 Bryce et a1. Feb. 16,1960

4. PAPER, 3-50% OF THE HYDROXYL OF THE CELLULOSE FIBERS OF WHICH HASBEEN REPLACED BY LOWER FATTY ACID RADICALS, WHICH PAPER HAS A POLYVINYLACETATE SURFACE SIZING WHICH CONTAINS HYDROXYETHYL CELLULOSE,PLASTICIZER AND WATERSOLUBLE WENER TYPE CHROMIUM COMPLEX IN WHICH ATRIVALENT NUCLEAR CHROMIUM ATOM IS CO-ORDINATED WITH AN ACYCLICCARBOXYLIC ACID GROUP HAVING AT LEAST 10 CARBON ATOMS, AND A COPATINGTHEREON OF BARIUM SULFATE AND GELATIN.